How to Prevent Firefox From Using Too Much Memory

Stop your browser from consuming too many system resources

Mozilla's Firefox browser does an excellent job providing stable, fast performance with a minimal memory footprint. But there may be times when Firefox uses too much memory and requires user intervention to increase both browser and system-based performance.

Here's how to prevent Firefox from using too much memory, using tactics such as starting in safe mode, removing extensions, and more.

This article's information applies to the Mozilla Firefox web browser on Windows, macOS, and Linux computers.

How to Prevent Firefox from Using Too Much Memory

Firefox Usage Best Practices

First, take simple, common-sense steps to be mindful of Firefox's resources. For example, close tabs you don't need open, and if you're using Firefox on a Windows PC, update your graphics drivers.

Firefox's built-in Task Manager lets you see which tabs or extensions are using a lot of memory or energy, so it's a great way to monitor how much memory the browser is using.

Make sure you're running the latest version of Firefox, and close other resource-intensive applications when you're using the browser.

Firefox's about:memory page lets you troubleshoot memory issues. Type about.memory into the Firefox search bar to generate memory reports and minimize memory usage.

How to Update Firefox

Updating Firefox is always a good idea. You'll install new security patches and take advantage of any performance enhancements. If there were a bug causing memory leaks, updating Firefox could eliminate the issue.

  1. Select the Menu icon (three horizontal lines) in the top-right corner.

  2. Select Options on the dropdown menu. (On a Mac, select Preferences.)

    Select Options in Firefox
  3. The Preferences page opens with the General category loaded by default. Scroll down to Firefox Updates.

  4. Select Check for updates.

    Check for updates in Firefox

    Here you can choose to manage update settings, such as enabling automatic updates or checking for updates and installing them manually. Firefox uses background services and updates search engines by default.

  5. Restart Firefox if needed.

Check for Resource-Hogging Extensions and Themes

If you're using any extensions or themes, see if they're causing performance issues. This process requires loading Firefox in Safe Mode.

  1. Type about:support in the address bar and press Enter or Return.

  2. Under Try Safe Mode, select Restart with Add-ons Disabled.

    Restart Firefox with add-ons disabled
  3. Select Start in Safe mode when Firefox restarts.

  4. Use Firefox as usual while checking your memory and CPU percentage. 

    If memory or CPU usage is still high, then extensions and themes aren't the problem. If the numbers remain low, disable themes and extensions.

How to Disable Firefox Extensions

Disable all extensions to see if the memory issue clears. If it does, re-enable each extension one at a time to determine the offending, memory-gulping addition.

  1. Select the Menu icon (three horizontal lines) in the top-right corner.

  2. Select Add-ons from the dropdown menu.

    Select Add-ons in Firefox
  3. Select Extensions in the menu on the left.

  4. Select the three-dot icon next to an extension.

  5. Select Disable on the dropdown menu. Repeat this process for each extension.

    Disable add-ons in Firefox

How to Disable Firefox Themes

If an extension isn't your memory-hogging issue, a downloaded theme could be the problem. Revert to the default theme and see if system performance improves.

  1. Select the Menu icon (three horizontal lines) in the top-right corner.

  2. Select Add-ons from the dropdown menu.

    Select Add-ons in Firefox
  3. Select Themes in the menu on the left.

  4. Under Disabled, select the three-dot button next to Default.

  5. Select Enable on the popup menu. You've restored the default theme.

    Enable the default theme in Firefox

How to Toggle off Hardware Acceleration

Hardware acceleration means Firefox dumps page rendering and other tasks onto your PC's hardware for faster performance. But hardware acceleration may cause problems, depending on your configuration. Turn off hardware acceleration and see if this improves system performance.

  1. Select the Menu icon (three horizontal lines) in the top-right corner.

  2. Select Options from the dropdown menu. (On a Mac, select Preferences.)

    Select Options in Firefox
  3. The Preferences page opens with the General category loaded by default. Scroll down to Performance.

  4. By default, Firefox enables the Use recommended performance settings option. Click to uncheck.

  5. Uncheck the Use hardware acceleration when available feature. See if your system performance improves.

    Tweak the performance in Firefox

    Here you can also change the content process limit. A higher number means better performance when running multiple tabs at the cost of additional memory. Eight is the default setting, but if you're experiencing memory issues, try lowering the process number.

Use the Built-in Memory Tool

Firefox provides a built-in tool to show memory reports and save logs. It allows you to clear memory and minimize memory usage.

  1. Type about:memory in the address bar and press Enter or Return.

  2. Locate the Free memory panel and select Minimize memory usage.

    Manually free memory in Firefox
  3. Optionally, you can select the GC (garbage collection) and CC (cycle collection) buttons.

How to Install the Auto Tab Discard Firefox Extension

While too many extensions can lead to memory issues, the Auto Tab Discard extension is designed to ease memory troubles. This extension suspends inactive tabs after a specific period of time. Here's how to install Auto Tab Discard.

  1. Head to the Auto Tab Discard listing on Mozilla's Firefox Add-ons page.

  2. Select Add to Firefox.

    Add the Auto Tab Discard extension
  3. Select Add in the in-browser popup window that appears.

    Add the Auto Tab Discard extension
  4. Click Okay, Got It to confirm the add-on management instructions. You'll now see a power button icon located next to the Firebox menu button.

    Suspend tabs with Auto Tab Discard
  5. Select Auto Tab Discard to access quick commands to close the current tab, close other tabs in the current window, and more.

    The Options section provides settings for discarding options, conditions, and exceptions.

Reduce Firefox Session History

One possible memory hog is your Firefox session history. Click and hold on the browser's back and forward buttons and you'll see a history of the sites you've visited. The maximum per-session history limit is 50, meaning Firefox stores 50 webpage addresses in memory. Since you're unlikely to rewind and fast-forward through this lengthy list, decrease that number to reduce Firefox's memory footprint.

  1. Type about:config in the address bar and press Enter or Return.

  2. Type browser.sessionhistory.max_entries in the search field and press Enter or Return.

  3. Double-click on the current value (50).

  4. Enter a lower number in the popup window's text field.

    Reduce the session history in Firefox
  5. Select OK.

Delete the content-prefs.sqlite File

The file storing individual website data may be corrupt. Delete the content-prefs.sqlite file and Firefox will create another once it restarts. This may solve your memory issues.

  1. Type about:support in the address bar and press Enter or Return.

  2. Under the Application Basics, next to Profile Folder, select Show in Finder. A window will open that contains your profile folder.

  3. Quit Firefox. In your profile folder, delete the file content-prefs.sqlite. It will be recreated next time you open Firefox.

Refresh Firefox

If nothing else seems to be solving the problem of Firefox using too many memory resources, try resetting Firefox to its original settings.

  1. Type about:support in the address bar and press Enter or Return.

  2. Select Refresh Firefox.

    Click the Refresh Firefox button
  3. Select Refresh Firefox in the confirmation popup.

    Refresh Firefox
  4. Select Finish when Firefox restarts.